According to the Metro Development Study (1995 - 1999), the approved Athens Metro Development Plan provided for the construction of two new Extensions, which would, in essence, be branches of the existing Lines, namely: Line 2 branch (Panepistimio-Exarhia-Alexandras-Dikastiria-Kypseli-Galatsi-Alsos Veikou) and Line 3 branch (Panormou-Faros-Sidera-OAKA-Paradissos-Maroussi). During the preparation of the Preliminary Designs of the aforementioned Projects, it turned out that due to technical reasons the said extensions could not be branches of the existing Lines, since this scenario would have important construction and operational deficiencies (interruption of line operation, complex construction, high cost, frequency of trips, etc.).

In this framework, ATTIKO METRO S.A. proceeded with the design and organization of the interconnection of the said extensions and their development as a new autonomous U-shaped Line 4, which shall include the two aforementioned radial branches (Panepistimio - Galatsi and Katehaki - Maroussi) and a central section connecting these radial branches through the areas of Pangrati/Kaissariani, Ano Ilissia, Zografou and Goudi. Line 4 shall ensure transfer to the existing Line 1 (at MAROUSSI, PERISSOS Stations), Line 2 (at PANEPISTIMIO Station) and Line 3 (at EVANGELISMOS & KATEHAKI Stations). Evangelismos - Pangrati - Vyronas - Ymittos – Ano Ilioupoli branch (which actually constitutes part of the new Line 5), as well as Maroussi - Lycovryssi and Alsos Veikou - Perissos extensions were added to this Line.

Line 4, this new 32 km long Metro Line, has 30 new modern state-of-the-art stations with automatic driveless trains, with platform screen doors, CTBC wireless signaling system, energy-saving advanced technology systems, etc.. The total cost estimate for construction works rises to 3.3 billion euros, while it is anticipated to alter dramatically the transportation map of Athens, and to upgrade significantly life in Attica Basin.

The Ministry of Infrastructures, Transport and Networks, in cooperation with ATTIKO METRO S.A., have prepared all necessary designs for the new Athens Metro Line 4 (30 stations – 32km), where provision is made for the partial tendering of the Project in five (5) phases (A – E). On September 25th 2014, the implementation and tendering of the first section of Line 4 (section A, Alsos Veikou – Goudi) –on a priority basis- was announced, including 14 stations, of a total budget of 1.2 billion Euros.

More specifically, the first section of Line 4 (section “A”) shall be 11.7 km long, including 14 stations (Alsos Veikou – Galatsi – Kypseli – Dikastiria – L. Alexandras – Exarchia – Akadimia – Kolonaki – Evangelismos – Kaisariani – Near East – Ilissia – Zografou – Goudi), and its budget is estimated to amount to 1.2 billion Euros. This section is foreseen to serve 220,000 passengers on a daily basis and shall reduce the daily number of circulating private vehicles by 53,000. At the same time, CO2 emissions are expected to be reduced by 279 tons/day. It will take approximately 10 min to travel from Alsos Veikou to the city centre, and approximately 5min from Zografou area to the city centre.

The Project double-track tunnels shall be bored using TBM (9.5m diameter), while the 110m long stations shall be constructed by applying the C/C method, the NATM underground boring method and their combination. The new line shall be connected through a single track tunnel with the existing tunnel connecting Lines 2 & 3 in Syntagma area, so that the new trains can be directed to the existing Depots. The scope of the Project includes the construction of underground stabling areas, a washing plant and a light repair workshop behind ALSO VEIKOU Station, the extension of Sepolia Depot maintenance and repair workshops, as well as the construction of a new Operations Control Centre for all Metro lines in Sepolia Depot area. During the construction of the Project, approximately 3,500 job positions shall be created.

The construction of the new Metro Line 4 presents significant advantages, such as:

To provide transportation service to many new densely populated areas of the city (Galatsi, Kypseli, Pangrati, Kaissariani, Ilissia, Zografou, Goudi, Vyronas). It is estimated that the new Line will serve more than 530,000 passengers on a daily basis.

To provide transportation services to many important facilities, such as Hospitals (Hospital for Children, “Laiko” Hospital, 401 Military Hospital, 251 Air Force General Hospital, Ygeia Hospital, Mitera Hospital, Iatriko Kentro Hospital), University Foundations (National Technical University of Athens (NTUA) in the city centre, University of Athens in the city centre, Law School, Technical University Campus, University Campus, School of Dentristry), the Courts area, regions with increased professional and commercial activities (city centre, Kifissias Avenue), and the Olympic Stadium facilities etc.

To increase the Metro branches with 5 transfer stations to Lines 1, 2 and 3.

To ‘decongest' the existing Metro stations, where there is a constantly increasing number of passengers (Syntagma, etc.).